1. Field of the Invention
This invention relates to the cleaning of furnace tubes. More particularly, it relates to reducing the amount of solids waste generated in the in-situ cleaning of furnace tubes.
2. Description of the Prior Art
In the hydrocarbon furnaces located in various refineries and petrochemical plants, it is necessary to remove coke deposits from the inner walls of furnace tubes. Such deposits form and grow during continuous operations leading to excessive pressure drop across the tubes, reduced throughput therein and reduced thermal efficiency of the furnace. While mechanical cleaning, hydroblasting and steam-air decoking are techniques known in the art for such internal furnace tube cleaning purposes, the in-situ cleaning of furnace tubes and other such conduits by the passage therethrough of steel shot or other cleaning particles entrained in a propelling gas stream is a highly advantageous and desirable approach. In-situ cleaning operations can be carried out, in batch-type cleaning runs, without disassembling the furnace and, particularly by the use of steel shot, without appreciable erosion of the return bend portions of the furnace tubes, and without the furnace cool downs required for other cleaning approaches.
Because of these and other advantages, the in-situ cleaning and decoking of furnace tubes and other pipelines is carried out as part of the Sandjet.RTM. in-situ cleaning process service activity of Union Carbide Industrial Services Company. In this in-situ process, cleaning particles are entrained in a propelling gas stream, preferably a nitrogen stream, and passed through the line, e.g. a bank of furnace tubes commonly oriented in a serpentine configuration. For furnace tube operations, the cleaning particles are desirably impact resistant, non-angular non-abrasive particles, such as steel shot, that effectively remove coke deposits from the internal walls of the furnace tubes by impact rather than by grinding or abrasion-type cleaning action. In this cleaning approach, further described in the Nunciato et al. patent, U.S. Pat. No. 4,297,147, the steel shot or like cleaning particles being passed through the furnace tubes have turbulent and swirl velocity components induced therein, causing them to strike the coke deposits with sufficient energy to dislodge chunks of coke that are swept from the furnace tubes by the propelling gas stream, along with the cleaning particles and loose coke debris. Such in-situ decoking enables the internal walls of the furnace tubes to be effectively cleaned, as in the more difficult to clean straight sections, without undue erosion of the return bend portions of the furnace tubes.
It will be appreciated that commercial in-situ furnace tube cleaning applications produce a considerable amount of waste material, including the coke removed from the furnace tubes and steel shot or other cleaning particles used in the cleaning process. The amount of waste varies with the size of the furnace, but is typically in the range of 1-3 tons per furnace cleaning. As landfill regulations become more stringent, solids waste disposal is an increasingly more difficult problem. There is a genuine need in the art, therefore, to reduce the amount of solids waste requiring disposal, and, in particular, it is highly desirable to reduce the amount of solids waste disposal associated with in-situ furnace tube cleaning operations.
It is an object of the invention, therefore, to provide an improved system for the in-situ cleaning of lines with minimized generation of solids waste requiring disposal.
It is another object of the invention to provide a system for achieving a significant reduction in the amount of solids waste to be disposed of as a result of the in-situ cleaning of pipelines.
With these and other objects in mind, the invention is hereinafter described in detail, the novel features thereof being particularly pointed out in the appended claims.